Numerous devices are known that enable a filling spout to be actuated in a packaging machine. Most such devices include a control member passing through the wall of the filling spout so that it is necessary to provide sealing to prevent the substance being packaged from leaking out where the control member passes through the wall.
Providing such sealing poses difficult problems when the substances to be packaged are abrasive or chemically aggressive, because there is then a danger that the sealing gaskets might be degraded rapidly if the material used for the gaskets is not compatible with the substance being packaged. Major problems also arise when substances are to be packaged in sterile manner, because they must be protected from being polluted by the control devices passing through the wall. Such protection requires complex devices that use vapor barriers or sterile-fluid barriers.
To avoid the necessity of having a control member that passes through the filling spout, Document U.S. Pat. No. 4,940,207 discloses a control valve including a valve member connected to a solid cylindrical magnetic core disposed coaxially inside a non-magnetic tubular body, the position of the valve member being controlled from the outside by using a magnetic field. Unfortunately, such a device suffers from the drawback that the substance to be dispensed flows between the magnetic core and the wall of the tubular body. This means that, to achieve a force that is large enough to raise the valve member, the flow must be limited if the distance between the outside surface of the magnetic core and the magnetic field generator is to be limited.